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Abstract #0044

Diffusion Weighted Magnetic Resonance Imaging for Pathological Response Prediction After Neo-Adjuvant Radiochemotherapy for Locally Advanced Rectal Cancer.

Martijn Intven1, Onne Reerink1, Marielle E.P. Philippens1

1Radiation Oncology, UMC Utrecht, Utrecht, Netherlands

Standard therapy for rectal cancer is neo-adjuvant therapy followed by resection. Evidence for organ-sparing therapy for good treatment responders after neo-adjuvant therapy is growing. Reliable selection of candidates for organ-sparing treatment is vital to prevent undertreatment of patients. In this study in 44 patients the predictive potential of diffusion-weighted MR Imaging for the selection of favorable responders was assessed. Both low pre-therapy ADC values and high relative ADC change (ADC) after neo-adjuvant therapy corresponded with pathological good response. The positive predictive value for predicting a good response was 89% for the ADC.